1. Field of the Invention
The present invention relates to a fail-safe air flap control apparatus for a vehicle which is constructed so as to prevent an air flap from stopping in a closed state when malfunctioning
2. Description of Related Art
Generally, a water-cooled type engine cooling apparatus includes a water jacket, a water pump, a radiator, a fan and a thermostat. The water jacket surrounds the cylinders and combustion chamber of the engine. The water pump supplies water into the cylinders under pressure to circulate it around the cylinders. The radiator transfers heat of coolant, which has been heated, to the air. The fan assists the heat exchange of the radiator. The thermostat is used to rapidly increase the temperature of the coolant to a predetermined degree just after the engine starts.
In the water-cooled type engine cooling apparatus, a coolant flow channel is formed in a cylinder block and a cylinder head of the engine, and parts of the engine are cooled by passing water through the coolant flow channel. The coolant (water) which has cooled the cylinder block is forcibly sent to the radiator through a radiator hose by the water pump which is operated by a crankshaft pulley. The coolant which has entered the radiator dissipates heat through the radiator and is supplied to the engine again to cool the engine.
The radiator is a kind of tank which has a large heat dissipation area and is able to contain a large quantity of water. The radiator includes a pipe through which water passes, and fins which are in contact with the air and function to increase the heat dissipation area to dissipate into the air as much heat as possible. Furthermore, a radiator grill is provided on a predetermined portion of a front bumper of the vehicle to separate the radiator from the outside of the vehicle and improve the appearance of the vehicle.
The radiator grill functions to maintain a flow rate of air drawn into the vehicle therethrough constant and to physically protect the radiator from foreign substances contained in the air which is drawn into the vehicle.
Meanwhile, recently, a technique in which a flap control apparatus is installed between the radiator grill and the radiator to appropriately control the flow rate of air supplied into the radiator through the radiator grill depending on the temperature of the coolant of the engine was proposed. In this technique, before warming-up of the engine is completed, the flap control apparatus restrains air from being supplied to the radiator, thus reducing the time taken to complete the warming-up.
FIG. 1 is an exploded perspective view illustrating the structure supplying air to a radiator, according to a conventional technique.
As shown in FIG. 1, a radiator grill 11 is installed on a front bumper 10 of a vehicle. A cooling module 20, such as a radiator and an air conditioning condenser, is disposed behind the radiator grill 11.
The cooling module 20 is assembled with a carrier 21. An air flap control apparatus 30 is installed between the cooling module 20 and the radiator grill 11. The air flap control apparatus 30 functions to control the flow rate of air supplied to the cooling module 20 through the radiator grill 11.
When the temperature of a coolant of the engine is relatively low, because the engine must rapidly complete warming-up, the flap control apparatus 30 is closed to reduce the flow rate of air supplied to the cooling module 20 such that the temperature of the engine can be rapidly increased. After the warming-up of the engine is completed, the air flap control apparatus 30 is opened to increase the flow rate of air supplied to the cooling module 20 such that the cooling performance is increased.
Typically, an actuator or a solenoid is used as a drive unit to operate air flaps of the air flap control apparatus 30. However, when the actuator malfunctions because of, for example, breaking of a wire or a short circuit, the air flaps are stopped in the state they were in when the malfunction occurred. Hence, if the actuator malfunctions when the air flaps are in the closed state, air cannot be supplied to the cooling module despite completion of the warming-up of the engine, resulting in a severe engine cooling problem.
Furthermore, in the case where the solenoid is used as the drive unit to operate the air flaps, because the solenoid is operated in such a way as to close the air flaps using adhesive force generated when power is supplied thereto, if the solenoid malfunctions, the adhesive force is eliminated so that the air flaps go into an openable state.
However, when the solenoid malfunctions, the air flaps can be opened only by air drawn thereinto while the vehicle travels. Therefore, when the vehicle is not moving but the engine is being operated, the cooling performance is largely reduced. In addition, although the vehicle is moving, because the speed at which the vehicle runs is variable, the air flaps cannot maintain the completely opened state but continuously flap.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.